Molded filter leaf

ABSTRACT

A double-faced filter leaf formed from two flat, molded sections joined back-to-back. Drainage channels are formed between parallel ribs molded on the front face of each section. A collecting channel transversely intersecting the drainage channels is also formed on the front face adjacent one edge of the leaf. Conduits for applying vacuum and removing filtrate are provided between the sections by opposed grooves formed on the back faces thereof. The conduits extend the full length of the leaf and are in communication with the drainage channels on the front face through one or more ports. Means are provided to hold a filter medium in place over the ribs.

0 United States Patent [151 3,679,06 1

Davis 1 July 25, 1972 [541 MOLDED FILTER LEAF FOREIGN PATENTS ORAPPLICATIONS [72] Inventor: Steven S. Davis, Bo tiful Utah 646,0317/1962 Canada ..2l0/33l 1,013,866 12/1965 Great Britain ..210/487 [73]Asslgneez Envirotech Corporation, Salt Lake City,

Utah Primary Examiner-Reuben Friedman Assistant Examiner-Frederick F.Calvetti [22] Ffled' June 1970 Att0rney--R0bert R. Finch and Richard F.Bojanowski [21] Appl. No.: 46,330

[57] ABSTRACT A double-faced filter leaf formed from two flat moldedsec- 52 U.S. Cl Int Cl trons joined back-to-back. Drainage channels areformed F between parallel ribs molded on the from face of each Section[58] lEldO Search ..2l0/33l, 346,486,487 A collecting channeltransversely intersecting the drainage channels is also formed on thefront face adjacent one edge of References Cited the leaf. Conduits forapplying vacuum and removing filtrate are provided between the sectionsby opposed grooves formed UNITED STATES PATENTS on the back facesthereof. The conduits extend the full length of the leaf and are incommunication with the drainage chan- 3,263,819 8/1966 Schmidt et a1...210/486 nels on the from face through one or more ports Means areprovided to hold a filter medium in place over the ribs.

9 Claims, 6 Drawing Figures l9 19 I9 I Q 5 1 1 *1 11 L 1: i i R I! 31 11/ PATENTEflJulzs m2 INYENTOR. Steven S. Davis BY Mag/MA,

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His Afforney MOLDED FILTER LEAF BACKGROUND OF THE INVENTION A hangingdouble-faced filter leaf is conventionally a thin hollow shell havingopposite faces of perforated metal or screen and overlain by a filtermedium. Vacuum is applied to the interior of the shell and filtrateremoved therefrom by dip tubes extending into the bottom portion of theshell. Filter cake formed on the filter medium is discharged by reducingthe applied vacuum, by blow back and/or by scraping.

A disadvantage of the hollow leaf structure is that solids siftingthrough the filter medium often block the screen. When this occurs,portions of the leaf become ineffective and eventually the filter mediummust be removed and the screen subjected to a costly, time-consumingcleaning operation.

An additional disadvantage of hollow leafs is their relatively highconstruction costs since they must be assembled from several parts suchas a frame, screen, dip tube and supports.

By forming the filter leaf from two molded sections rather than castingthe leaf as a single piece, drilling of vacuum conduits and/or otherintricate machining operations are eliminated.

OBJECTS OF THE INVENTION A primary object of the invention is to providea filtration device comprising a solid filter leaf formed from two solidmolded pieces having only surface drainage channels underlying thefilter medium, thus eliminating the use of a screen and the attendantproblems of blockage and cleanup associated therewith.

Another important object is to provide a leaf structure which is readilyadaptable to construction by molding, thus minimizing initialconstruction costs.

A related object is the provision of a symmetrical leaf design whichpermits the leaf to be formed from two identical pieces of sections,thereby requiring the use of only a single mold for manufacture.

SUMMARY OF THE INVENTION The foregoing and possibly other objects of theinvention are attained by a leaf construction having a pair of filteringfaces formed from two solid molded sections joined back-toback. Eachsection comprises an impervious web support having a plurality ofsubstantially parallel elongated channels intersecting with at least onecollecting channel which in turn communicates at the lower end of theleaf through ports with one or more conduits formed between the sectionsfor applying vacuum and withdrawing filtrate.

with the particular leaf construction of the invention, solids whichsift through a filter medium covering the web support will deposit onlyin the surface channels and cause only a slight reduction in filteringcapabilities. Moreover, the high liquid velocities which pass throughthe ports and the vacuum conduit, discourage solids from depositingtherein thus permitting the surface channels to be self-cleaned.However, should a solids buildup occur, it can usually be overcome byblow back. If this fails and if removal of the medium is required toremove the deposited solids, shut-down time is cut to a minimum as onlyexterior surfaces and a few ports require cleaning.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing afilter leaf without a filter medium embodying this invention.

FIG. 2 is a cross-sectional view taken in the plane of line 2- 2 of FIG.1 looking in the direction of the arrows.

FIG. 3 is a cross-sectional view taken in the place of line 3 3 of FIG.I looking in the direction of the arrows.

FIG. 4 is a cross-sectional view taken in the plane of line 4- 4 of FIG.1 looking in the direction of the arrows.

FIG. 5 is a cross-sectional view taken in the plane of line 5 5 of FIG.1 looking in the direction of the arrows.

FIG. 6 is a perspective view illustrating a modified embodiment of thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 through 5 inwhich like elements are designated by the same reference numerals, thefilter leaf 12 comprises two sections 12a and 12b mounted back-to-backwith their exposed front faces being ribbed to provide drainage decks ashereinafter described. Each section and 12b is molded as a solid sectionfrom any suitable thermosetting or thermoplastic material to form animpervious front face 13 having a plurality of upstanding spaced ribs 17parallel to each other, two side edges 14 running parallel to the ribs,a top edge 15 and a bottom edge 16. Substantially parallel drainagechannels 18 are formed as a result of the spaces between the ribs. Asshown, the two vertical side edges 14 extend above the top edge 15 andare adapted for use as hangers to support the filter leaf. To provideadditional strength, a reinforcing member 31 may be molded into thevertical and top edges.

As used herein, the term impervious means that the filter face is notporous and does not contain any openings through which liquid may flow,with the exception of ports which are in communication with the tubularchannels later described.

The ribs 17 and channels 18 terminate short of the bottom edge 16 tointersect with and define a transverse collecting channel 18 bordered bythe bottom edge for receiving filtrate from the drainage channels. Aplurality of internal vacuum pipes 19 is formed between sections 12a and12b by concave grooves 20 molded in the back surfaces thereof. Asillustrated, the grooves are complementary or opposite each other sothat together they form a single conduit. However, it is not mandatorythat there be complemental or opposed grooves as it may be desirable tohave a semi-tubular conduit defined by one such groove and the flat backface of the other section.

Communication between the internal conduits and the filter surface isprovided by ports 21 which extend from the collecting channel 18 throughthe section into the conduits 19. In normal operation the upper ends ofthe conduits 19 will be in connection with any suitable vacuum source(not shown).

For assembly, the two sections (12a and 12b) are placed back-to-backthen either clamped or cemented together. The assembled leaf is thencovered with a suitable filter medium and retained thereon in knownmanner. For clarity purposes, the filter medium is not shown in thedrawings.

The filter leaf is designed and shaped to enable each section of theleaf to be molded as by injection molding in either a single or a numberof pieces, depending on leaf size. In this connection, the channels andgrooves are smoothly concave and contain no undercuts, thus facilitatingremoval from a mold. In addition, this type of shape and design resultsin unhampered drainage flow.

In operation, filtrate passes through the filter medium into the surfacechannels thence downwardly, as shown by the arrows to the collectingchannel whence it flows through the ports 21 into the vacuum tubes 19.Cake forms on a filter medium covering both outer faces and isdischarged either by scraping, by pressure changes, or both.

If desired, horizontal strips may be fastened over the top of thevertical ribs in the FIG. l5 structure as an aid in supporting thefilter medium heavy with cake.

FIG. 6 shows a particular embodiment of the invention wherein thesurface channels 29 are formed by horizontal ribs 28 rather than byvertical ribs. In this case the intersecting collection channels 32 arevertical and border side edges 33 and/or a raised center section 34.Ultimately, they are in communication with an internal vacuum tube 30through ports 35. Arrows show the direction of liquid flow. Thehorizontal ribs aid in holding the cake and filter medium in place;hence, this design is especially useful with dense or slippery cakes.

Although the invention has been described with reference to specificembodiments, it is not intended that the invention be limited theretobut to include all the variations and modifications falling within thescope of the appended claims.

What is claimed is:

1. A double-faced filter leaf construction having top, bottom and sideedges comprising two solid impervious substantially flat molded sectionsjoined together in back-to-back relationship, a plurality of parallelribs on each face of said leaf forming drainage channels therebetween, acollection channel formed on each face to transversely intersect saiddrainage channels, at least one elongated internal vacuum tube formed bya groove in the back surface of at least one of said sections andextending longitudinally thereof between and parallel to said faces,said internal vacuum tube being in communication with said collectionchannel and extending upward to the top edge of said leaf, and portmeans in said leaf located substantially near the junction of saidcollection channel and said vacuum tube, said port means constitutingthe sole communication between the collection channel and the vacuumtube.

2. A construction according to preceding claim 1 in which said drainagechannels are formed between parallel ribs running longitudinally of saidleaf and said collection channel is transverse to said drainage channeland is formed between the ends of said ribs and the bottom edge on saidleaf.

3. A construction according to preceding claim 2 in which said surfacechannels are concave and said elongated internal vacuum tube is formedby a pair of opposed grooves in the back side of each section.

4. A construction according to preceding claim 3 in which said sectionsare molded and said side edges are extended upward to form a means forhanging said leaf.

5. A construction according to preceding claim 4 in which saidimpervious sections are symmetrical in shape and design.

6. A construction according to preceding claim 5 in which a reinforcingmember is molded into said side and top edges.

7. A construction according to preceding claim 6 in which spacedhorizontal strips override said parallel ribs running longitudinally ofsaid leaf.

8. A construction according to claim 6 in which a filter mediumoverrides the faces of said leaf.

9. A construction according to claim 1 in which said drainage channelsare formed between parallel horizontal ribs and intersect with at leastone vertical drainage channel.

1. A double-faced filter leaf construction having top, bottom and sideedges comprising two solid impervious substantially flat molded sectionsjoined together in back-to-back relationship, a plurality of parallelribs on each face of said leaf forming drainage channels therebetween, acollection channel formed on each face to transversely intersect saiddrainage channels, at least one elongated internal vacuum tube formed bya groove in the back surface of at least one of said sections andextending longitudinally thereof between and parallel to said faces,said internal vacuum tube being in communication with said collectionchannel and extending upward to the top edge of said leaf, and portmeans in said leaf located substantially near the junction of saidcollection channel and said vacuum tube, said port means constitutingthe sole communication between the collection channel and the vacuumtube.
 2. A construction according to preceding claim 1 in which saiddrainage channels are formed between parallel ribs runninglongitudinally of said leaf and said collection channel is transverse tosaid drainage channel and is formed between the ends of said ribs andthe bottom edge on said leaf.
 3. A construction according to precedingclaim 2 in which said surface channels are concave and said elongatedinternal vacuum tube is formed by a pair of opposed grooves in the backside of each section.
 4. A construction according to preceding claim 3in which said sections are molded and said side edges are extendedupward to form a means for hanging said leaf.
 5. A constructionaccording to preceding claim 4 in which said impervious sections aresymmetrical in shape and design.
 6. A construction according topreceding claim 5 in which a reinforcing member is molded into said sideand top edges.
 7. A construction according to preceding claim 6 in whichspaced horizontal strips override said parallel ribs runninglongitudinally of said leaf.
 8. A construction according to claim 6 inwhich a filter medium overrides the faces of said leaf.
 9. Aconstruction according to claim 1 in which said drainage channels areformed between parallel horizontal ribs and intersect with at least onevertical drainage channel.